This invention relates to accumulating conveyors, and more particularly to a control system for an accumulating conveyor which is operable to sequentially initiate operation of adjacent conveyor zones.
An accumulating conveyor generally includes a series of zones which can be selectively controlled to allow articles being conveyed to accumulate in a selected area of the conveyor. Examples of control systems for providing certain functions of an accumulating conveyor are disclosed in Hall U.S. Pat. No. 5,255,558 issued Jul. 20, 1993 and Hall U.S. Pat. No. 5,285,887 issued Feb. 15, 1994.
Methods for operating accumulating conveyors have been well established over the years. One such method is known as singulated release, which controls the conveyor zones such that a load is discharged from one zone only when the immediately adjacent downstream zone is empty. Singulated release control is generally used to fill accumulating conveyors and to operate as a normal transport mode. This type of control is a very straight forward approach which can be accomplished using air logic, mechanical switches, combinations of clutches and brakes, or individually powered conveyor sections. Another conveyor control method is known as train release, which is operable to run multiple zones simultaneously regardless of whether or not there is a load on the zone. Train release is typically used near the discharge end of an accumulating conveyor to provide a large quantity of objects in rapid succession.
In the train release mode of operation, discharge of a load from the downstream end of the system can result in simultaneous start-up of all zones upstream therefrom. In some installations, such as in a suspended conveyor system, this simultaneous start-up of all conveyor zones may result in a mechanical resonance of the conveyor zones, resulting in the potential for mechanical damage to the structure of the conveyor as well as other problems. Further, simultaneous start-up of all conveyor zones results in a significant power surge on the electrical supply system. In addition, simultaneous start-up of all conveyor zones results in simultaneous stopping of all zones when the conveyor system initiates accumulation, which again can result in mechanical resonance of the system.
It is an object of the present invention to eliminate the potential for resonance in an accumulating conveyor system upon start-up and stopping of the conveyor zones. It is a further object of the invention to provide such a conveyor control which alleviates the potential for a sudden power drain on the electrical system for the accumulating conveyor upon start-up of the conveyor zones. Another object of the invention is to provide such a conveyor control which is relatively simple in its operation and easy to implement for use in conventional conveyor control systems.
In accordance with the invention, a conveyor system for transporting a series of loads includes a series of conveyor zones which includes at least an upstream conveyor zone and a downstream conveyor zone. A drive arrangement is interconnected with each conveyor zone for operating each conveyor zone to advance loads along the conveyor system. The invention contemplates a control arrangement interconnected with each drive arrangement, with the control arrangement being operable to stop operation of both the upstream and downstream conveyor zones to maintain stationary any loads carried by the upstream and downstream conveyor zones, to accumulate loads thereon. The control arrangement is operable to sequentially resume operation of the upstream and downstream conveyor zones by first initiating operation of the downstream conveyor zone and subsequently initiating operation of the upstream conveyor zone after a predetermined time delay from initiation of operation of the downstream conveyor zone. In this manner, the conveyor zones are started up sequentially, to effect a sequential or "wave" release of loads carried by the conveyor zones. In a preferred form, the control arrangement includes an individual control module for each of the upstream and downstream conveyor zones. The control modules of the upstream and downstream conveyor zones are interconnected with each other such that the control module of the upstream conveyor zone continuously monitors the status of the control module of the downstream conveyor zone. The control module of the upstream conveyor zone is operable to initiate operation of the upstream conveyor zone subsequent to operation of the downstream conveyor zone by receiving a permission signal from the control module of the downstream conveyor zone after the predetermined time period has lapsed from initiation of operation of the downstream conveyor zone. The upstream conveyor zone may be one of a series of conveyor zones upstream of the downstream conveyor zone. The control arrangement is interconnected with the drive arrangement of each of the upstream conveyor zones, to sequentially initiate operation of each of the upstream conveyor zones after a predetermined time delay from initiation of operation of the conveyor zone downstream therefrom.
The invention further contemplates a method of controlling a conveyor having adjacent upstream and downstream conveyor zones for advancing a series of loads, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.